Electronic apparatus



June 27, 1944.

Filed May 19, 1941 W. F. WOLFNER, 2D

ELECTRONIC APPARATUS jzz erezor' 444171307711? 744% n 3 Patented June27, 1944 UNITED STATES PATENT OFFICE 2,352,240 EIECTRONIC APPARATUSWilliam F. Woltner, I'I, Mcthuen, Mass, assignor to PhotoswitchIncorporated, Cambridge, Mass., a corporation of MassachusettsApplication May is, 1941, Serial No. 394,232 2 Claims. (oi. can-41.5)

This invention deals with electronic apparatus of the glow dischargetype, and particularly with the utilization of such apparatus foroperating detecting, control, relay or similar electric apparatus.

As well know electronic tubes of this type comprise in addition tocathode and anode in a gas filled envelope, a control electrode orstarter anode which initiates current flow through the tube if a certainpotential is applied to the control electrode, whereupon the tubebecomes fully conductive whereas, if supplied with alternating current,it is substantially non-conductive so long as the potential level of thecontrol electrode remains below that value; if it is supplied withdirect current, the tube will remain conductive so long as an efiectivepotential difference is applied to cathode and anode.

It is the object of the invention to provide a very sensitive and yetreliable circuit incorporating such tubes which is easily adaptable tovarying operating conditions and especially suitable for detecting suchoperating conditions, as for example the burning of a flame, with thesimplest possible means requiring low cost of operation and maintenance.

Although other tubes can be used for this purpose, I prefer to employglow-discharge tubes with cold cathode which require practically noenergy while being held in readiness for operation and which, duringoperation with alternating current, consume only a small amount ofcontrol energy supplied to cathode and control electrode for eilecting aglow discharge and hence an ionized current path between cathode andcontrol electrode, which path renders and maintains the tube conductive.

According to an important aspect of the invention, I connect such a tubedirectly to a current supply source in such a manner that the responsecan be determined exactly and with permanent adjustment independent ofthe load or tube current so that certain operation of a responsive orcontrol element such as a solenoid is insured; this arrangement maynormally provide or hold in readiness either the current path through orthe potential supply to cathode and starting anode, both of whichconditions are necessary for initiating current flow through the tubewhich will begin as soon as the additionally necessary potential orcurrent, respectively, are applied- By properly correlating detectingcircuit and tube characteristics it is even possible, according toanother aspect of the invention, to

neither current path nor potential supply initially in readiness butprovide both directly when the detecting circuit is conditioned formaking the circuit responsive. This last-mentioned modification is thesimplest possible circuit of this type and therefore especially valuableunder certain operating conditions.

These and other objects and aspects of my invention will be apparentfrom the following descriptions of several practical embodiments thereofby way of example, this description refers to a drawing showing in Figs.1 to 4 diagrams of these embodiments.

In Fig. 1 two line terminals a, 1) indicate a source of alternatingcurrent supplying a tube T (for example of R. C, A. type OA4-G) withcathode K, anode A and starting anode 8. Between anode A and terminal ais connected a controlled circuit with a load appliance, for examplerelay unit B. with magnet l and switch 4, 5 normally interrupting anactuating circuit ill connected to source a, b. A condenser 6 isconnected in parallel to magnet l in order to retain the latterenergized during the half cycles when the tube current is interrupted. Aresistance 1 is provided in series with condenser E, for the purpose oflimiting the peak current through 6 at the instance when tube T becomesconductive; without this resistance, condenser 6 would at that momentpractically short circuit the supply.

Connected between starting anode s and anode terminal a, and startinganode s and cathode terminal b is a controlling circuit with twoimpedances 20 and 30, respectively, one or both of which may bevariable. In the present instance both impedances are indicated asvariable, and in series therewith may be arranged switches 2| and 3!,respectively.

Theimpedances 20 and 30 can be so controlled that the control value ofthe potential difference between b and s is either higher or lower thanits starting value; one or both resistances may be rendered normallyinfinite by means of switches 2i and 3i. The control value of thecurrent flowing at any time through electrode s may likewise be higheror lower than the starting value, depending upon the operation of thecircuit in question, as will appear more clearly hereinafter.

Assuming, for example, that switches 2| and 3| are closed, impedances 20and 30 can be so correlated that the above-mentioned potentialdifierence between D and s will maintain tube T dispense with suchprovisions, that is, have so normally non-conductive. and r lay Rdeenergized, which condition is indicated by the nonglowing state of thetube.

It the potential level of s relatively to K is now raised to thestarting value by decreasing impedance relatively to impedance 30, thestarting energy can be applied since a starting current path is providedthrough 20; tube '1 becomes conductive and glowing, energizing magnet Iwhich closes switch 4.": of controlled circuit I0.

In certain practical instances it may be prefer.- able to render thetube conductive by closing normally open switch 2| with 3| closed, or byopening switch.3l while 2| remains closed. In the first instance,impedance 20 is normally infinite and the starting potential normallyavailable through impedance in the second instance, the tube will benormally conductive with a starting current path always provided byimpedance'2ll and the potential of s maintained sufliciently high due tothe infinite value of resistonce 30. By closing switch 3 I, thepotential level of s is reduced below the starting value, and tube Tbecomes non-conductive.

Circuits of the latter type are especially vainable for example forpurposes of flame control, and a practical arrangement of this characteris shown in Fig. 2. In this figure impedance 30 and switch 3| arerepresented by a detecting arrangement consisting of two probes M, 42extending into a flame 40. sioned with regard to the impedance of flamethat s, so long as the flame is burning, will be at a potential levellow enough to prevent tube T from becoming conductive. As soon as theflame is extinguished, the potential level of raises and since a currentpath is permanently provided through 20, the tube will become conductiveand relay R will energize circuit 10, for example for ringing an alarmor closing a fuel supply valve.

The control circuit may be continuously energized by providing, insteadof condenser 6 (Fig. 1), a split magnet l I with heavily shaded pole l2.

By taking proper safeguards according to another aspect of theinvention, the circuit can be operated without impedance 3D, and twosuch arrangements are shown in Figs. 3 and 4.

Fig. 3 illustrates a light sensitive arrangement, impedance 20 beingrepresented by a phototube 5| and a resistor 52 in parallel thereto; theother elements are the same as in Fig. l. The value of 52 is such thatthe current which is normally per mitted to pass through electrode 5'and cathode K is below the value sufiicient to supply the necessarystarting energy. It will be noted that the starting electrode may wellbe above the starting potential level without being able actually to,start the tube, since the current between s and K is kept below thevalue necessary for ionizing the ube.

In Fig. 3, when phototube 51 is illuminated and hence its impedancelowered, the current flowing between s and a will reach the startingvalue and tube T becomes conducting. Once the tube is The impedance 2i]so dimen started, the current passed by 52 will be sufficient tomaintain it conductive although the starting anode potential may dropbelow the starting value, until the supply circuit is interrupted, asfor example by means of switch 55. Hence, magnet I remains energizedeven if the phototube should again become essentially non-conductive,this alternating current circuit being suitable when commencement of asupervised condition is required to maintain energization of a controlcircuit regardless of the duration of that condition.

In Fig. 4, impedance 3D is permanently infinite; and impedance 20 andswitch 2! are represented by a phototube 5|; otherwise the circuit maybe similar to that of Figs. 1 or 2. So long as tube H is dark, neitherstarting potential nor starting current will be effective at s. If thephototube is of a suitable type and sufllciently illuminated to pass thestarting current, and to apply to s the potential necessary forstarting, tube T will become conductive and relay R energized. Thiscircuit, therefore, permits selection of its operating range merely bycorrelation of the characteristics of the two absolutely necessaryelements, namely detecting means .(as for example the photocell) andamplifying tube; no special setting or adjustment elements need beprovided and this equipment is, therefore, especially inexpensive andrugged.

It will now be apparent that circuit variations of the type of Fig. 1,with normally closed switches 21 and 3|, make control current flowthrough or control potential applied to electrode 8, or both, normallyavailable but normally maintain at least one of them below the startingvalue; that the type according to Fig. 2 makes the control currentnormally available and depends ior operation on the control potentiallevel 0! s; that the type according to Fig. 3 makes the controlpotential normally available and depends for operation mainly upon thecontrol current; and that the type according to Fig. 4 has normallyneither control current nor potential available so that the detectingelement has to provide both at their starting values before it canassume control of the circuit. It will also be apparent that some of theherein described embodiments of my invention can be operated with tubeswhose control element does not carry current and is effective merelythrough its potential level. Such tubes may, for example, be controlledby electrostatical elements outside of the tube envelope.

It will further be understood that suitable ohmic capacitive orinductive impedances will be used at 20 and 30, in accordance with thecharacter of the particular embodiment.

Still further, operation of these circuits with direct current ispossible, in which case initiation of a certain supervised conditionwill maintain the control circuit energized regardless of the durationof this condition; as pointed out above, the same mode of operation ispossible with alternating current if the modification according to Fig.3 is used.

It will finally be noted that the operation of these circuits isindependent of the load value since the critical potential differencebetween cathode and control electrode is independent of the tubeconductivity.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

I claim:

. 1. Electronic relay apparatus comprising an alternating currentsource, a gas filled electron nected to said source in series with saidanode and said cathode, a controlling circuit including a normally highcontrol impedance connected between said anode terminal and said starteranode and a comparatively low impedance parvalues of both potentialdifference, and current flowing, between said cathode and said starteranode exceed predetermined starting values respectively, a controlledcircuit including means responsive to the conductivity of said tube connected to said source in series with said anode and said cathode, acontrolling circuit including a phototube connected between said anodeter-.

minal and said starter anode and a resistor in parallel to saidphototube, said controlling circuit normally maintaining said potentialcontrol value and retaining said current control value below itsstarting value, and said current control value being raised above itsstarting value by decreasing th impedance of said phototube and henceincreasing the current flowing therethrough from said source, uponincreased illumination of the phototube.

WILLIAM F. WOLFNER, II.

